1. Technical Field
The present invention relates to a liquid ejecting head, a liquid ejecting apparatus, and a method for manufacturing a liquid ejecting head. More specifically, the present invention relates to a pressure chamber forming plate, compliance plate, and nozzle plate for a liquid ejecting head.
2. Related Art
One method currently used for forming a recording head comprises forming a ink jet recording head having a plurality of nozzle orifices capable of discharging ink using a laminating process in order to form a pressure chamber forming plate, a compliance plate, and a nozzle plate. The nozzle plate has a plurality of nozzle orifices arranged in a predetermined configuration. The pressure chamber forming plate forms a plurality of pressure chambers which respectively communicate with the plurality of nozzle orifices. The pressure chamber forming plate has a reservoir which communicates with each pressure chamber via an ink supply passage. The reservoir leads to an opening on the surface of the pressure chamber forming plate on the side of the compliance plate, which is covered by the compliance plate. Ink supplied to the reservoir, from an ink cartridge, for example, is supplied to each pressure chamber through an ink supply passage. Each pressure chamber is provided with a piezoelectric element. When a predetermined drive voltage is applied to one of the piezoelectric elements, the piezoelectric element is deformed (extended), and the pressure chamber is pressurized. As a result, the ink in the pressure chamber is pushed out through the corresponding nozzle orifice and discharged in the form of an ink droplet.
Ink supplied to the recording head, such as ink supplied from an ink cartridge, is temporarily stored in the reservoir before it is supplied to each pressure chamber. At this time, if a large amount of ink is supplied to the reservoir, an excessive pressure may be applied to the reservoir. As a result, ink may be oversupplied to each pressure chamber, and the unnecessary discharge of dots can occur. In order to alleviate this problem, the compliance plate has a recess formed on the side of the nozzle plate, in a portion corresponding to the location of the reservoir. Because of the recess, that portion of the compliance plate is thinner than the rest. Thus, when ink is supplied to the reservoir and the pressure in the reservoir is increased, the thin portion (called compliance portion) is pressed by the ink in the reservoir and bends toward the nozzle plate, thereby absorbing the increased pressure in the reservoir and preventing an erroneous discharge from occurring.
In one ink jet printer head currently known in the art described in Japanese Patent Application No. JP-A-2005-41047, a base plate where the pressure chambers are formed is made from a rolled metal plate where the rolling direction is parallel to the longitudinal direction of the pressure chambers. In another ink jet recording head described in Japanese Patent Application No. JP-A-2005-41047, the nozzle plate is formed from a rolled metal plate where the longitudinal direction of the planar profile is substantially perpendicular to the rolling direction.
Recently, attempts have been made to increase the number of nozzles and to reduce the size of the products. In order to successfully reduce the size of the products, the size of each plate of the recording head needs to be reduced. To reduce the size of each plate, it is necessary to reduce the area of the compliance portion. On the other hand, the amount of ink being supplied to the reservoir is increasing due to the above densification. Unfortunately, the rigidity of the thin portion is reduced when the thickness of the compliance plate reduced, meaning that the thin portion may be excessively bent in response to the pressure generated in the reservoir. As a result, a part of the bent thin portion can come into contact with the nozzle plate. Under such circumstances, the thin portion cannot serve as a pressure absorber
Each plate of the above recording head is made by rolling metal. Such rolled plates tend to warp in the rolling direction. Such warping of the plates results in the warping of the whole recording head. The warping of the recording head causes, for example, variation in the distance between the nozzles and a recording medium onto which dots are discharged. Thus, warped recording heads are defective products. This is a problem not only for ink jet recording heads that discharge ink but also for various liquid ejecting heads.